Words in Encrypted String

You are required to extract a specific word target_word from an encrypted document. Fortunately, you have the basic information needed to decrypt that document.

The equation used to encrypt the document is as follows:

$$E_n(x) = (I(\mathsf{s}) + n) \mod 26$$

Where:

• $\mathsf{s}$ is a letter
• $I(x)$ is the number representing the position of the letter in the alphabet (1 for A, 2 for B, etc.)
• $n$ is an arbitrary integer.
• $E_n(x)$ is the encrypted letter.

Return the number of occurrences of target_word in the document after decryption.

Note: The document only has upper case letters and spaces.

Example:

Input:

encrypted_document = 'WKH TXLFN EURZQ IRA MXPSV RYHU WKH ODCB GRJ'
n = 3
target_word = 'BROWN'

Output:

extract_word(encrypted_document,n,target_word) -> 1

Explanation:

After decrypting the document, you will have :

THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG

In which the target_word (BROWN) appears only once.